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The aim of the study was to evaluate the short and medium term use of personalised insoles, produced by combining additive manufacturing (AM) with three-dimensional (3-D) foot scanning and computer aided design (CAD) systems. For that, 38 runners (19 pairings) were recruited. The experimental conditions were: personalised and control. The personalised condition consisted of trainers fitted with personalised glove fit insoles manufactured using AM and using foot scans to match the plantar geometry of the feet. The control condition consisted of the same trainers fitted with insoles also manufactured using AM but using scans of the original insole shape. Participants were allocated to one of the experimental conditions and wore the trainers for 3 months. Over this period they attended three laboratory sessions (at months 0, 1.5 and 3) and completed an Activity Diary after each training session. The footwear was evaluated in terms of discomfort and biomechanics. Lower discomfort ratings were found in the heel area (P ≤ 0.05) and for overall fit (P ≤ 0.05), with the personalised insole. However, discomfort was reported under the arch region for both conditions. With regard to the biomechanical data, differences between conditions were detected for ankle dorsiflexion at footstrike (P ≤ 0.05), maximum ankle eversion (P ≤ 0.05) and peak mean pressure under the heel (P ≤ 0.01): the personalised condition had lower values which may reduce injury risk. The personalisation of the geometry of insoles through advances in AM together with 3-D scanning and CAD technologies can provide benefits and has potential.

Traditional methods for developing foot orthoses require extensive skilled manual labor. More modern methods have sought to address this with the introduction of computer enabled technologies such as digital scanning, computer aided design, and automated manufacturing. The current work further advances the process with the introduction of an additional computer enabled technology, simulation models, into two additional steps. First, a simulation model is used to achieve the postural adjustments to the foot normally done by a practitioner. This has the benefit of further automating the process, improving repeatability, and preventing the deformation of the plantar soft tissues that normally occurs with physical postural adjustment. Second, the simulation model is used in a routine to optimize plantar pressure distribution. When compared to a conventional method, the proposed approach yielded a 61% reduction in peak plantar pressure. Future work includes automating the optimization routines for a variety of metrics. Other applications for the current work include the development processes of orthoses and prostheses for other parts of the body.

BACKGROUND:
Custom foot orthoses are currently recognized as the gold standard for treatment of foot and lower limb pathology. While foam and plaster casting methods are most widely used in clinical practice, technology has emerged, permitting the use of 3D scanning, computer aided design (CAD) and computer aided manufacturing (CAM) for fabrication of foot molds and custom foot orthotic components. Adoption of 3D printing, as a form of CAM, requires further investigation for use as a clinical tool.This study provides a preliminary description of a new method to manufacture foot orthoses using a novel 3D scanner and printer and compare gait kinematic outputs from shod and traditional plaster casted orthotics.
FINDINGS:
One participant (male, 25 years) was included with no lower extremity injuries. Foot molds were created from both plaster casting and 3D scanning/printing methods. Custom foot orthoses were then fabricated from each mound. Lower body plug-in-gait with the Oxford Foot Model on the right foot was collected for both orthotic and control (shod) conditions. The medial longitudinal arch was measured using arch height index (AHI) where a decrease in AHI represented a drop in arch height. The lowest AHI was 21.2 mm in the running shoes, followed by 21.4 mm wearing the orthoses made using 3D scanning and printing, with the highest AHI of 22.0 mm while the participant wore the plaster casted orthoses.
CONCLUSION:
This preliminary study demonstrated a small increase in AHI with the 3D printing orthotic compared to the shod condition. A larger sample size may demonstrate significant patterns for the tested conditions.

Highlights
•Anatomical Insoles have been manufactured by techniques that produce wastes and lacks of flexibility for the designer.
•This paper presents a methodology intended for the functionalisation of anatomical insoles through a systematic approach.
•It shows how to specific CAD/CAE tools can obtain internal structures automatically by parametric design.
•The 3D geometry of the insole can adequately be processed so that it can be printed by FDM.
•A comparative study between traditional and FDM techniques that takes into account real-environment parameters is presented.

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Anatomical insoles and additions have a corrective action on the footwear user. They are intended to reduce and adequately distribute plantar pressure among support points, thus minimising the stress these points can undergo. Such customised components have traditionally been manufactured either handcrafted or by subtractive techniques, i.e. by milling a sheet of material. Latest advances in additive manufacturing (AM) techniques and, in particular, the popularisation of 3D printing by fused deposition modelling (FDM), have opened new ways for the production of anatomical insoles. These technologies allow additional functionalities to be added, as for instance the use of materials with antimicrobial properties, or, at a structural level, zonal control in 3D design to increase cushioning capacity. The latter cannot be achieved by traditional manufacturing techniques, in that the inside of the element is not accessible. However, there are no CAD tools available for the design and production of insoles, which are specifically oriented to take advantage of the benefits that AM can bring about. Based on a previous study about the possibilities for functionalisation of anatomical insole materials and structures, this paper intends to review certain CAD methodologies for the design and manufacture of insoles by means of additive manufacturing techniques. These techniques will be employed to design and produce prototypes through which it is possible to assess such techniques. In order to study the feasibility of using this technology for the manufacture of customised insoles in a real production environment, this paper presents a comparative analysis of the proposed technology and the technology that is currently being used.

Designs with adjustable gradient modulus have become necessary for applications with special demands such as diabetic insole, in which the contact stress between the foot and insole is a critical factor for ulcers development. However, since the adjustment of elastic modulus on certain regions of insole can hardly be achieved via materials selection, a porous structural unit with varying porosity becomes a feasible way. Therefore, porous structural units associated with adjustable effective modulus and porosity can be employed to construct such insoles by 3D printing manufacturing technology. This paper presents a study on the porous structural units in terms of the geometrical parameters, porosity, and their correlations with the effective modulus. To achieve this goal, finite element analyses were carried out on porous structural units, and mechanical tests were carried out on the 3D printed samples for validation purposes. In this case, the mathematical relationships between the effective modulus and the key geometrical parameters were derived and subsequently employed in the construction of an insole model. This study provides a generalized foundation of porous structural design and adjustable gradient modulus in application of diabetic insole, which can be equally applied to other designs with similar demands

With the increasing applications of 3D printing, podiatric research has received considerable attention from researchers worldwide. 3D-printed customized soles came into use to mitigate a patient foot’s pain and ameliorate comfortability. The presented work is aimed to provide customized foot sole with variable infills and appropriate depths in order to get the adequate pressure and comfort on the precise nerve areas, which are the origins of pain.In the proposed work, a 3D-sole is reconstructed conceptualizing variable infill density and appropriate depth fitting using foot plantar pressure measurements. The given work comprised of four phases: attaining foot plantar pressure readings, data processing, infill density distribution and 3D printing of the sole. Initially, the foot plantar data is obtained by a platform using an array of 32 X 32 piezo-electric sensors. Secondly, the input data is corrected with the removal of the rigid pattern from the foot sole via median filtering and interpolated via bicubic interpolation to obtain the smooth surface. Thereafter, modifiers are created to dispense different densities to distinct portions of the model. At last, the model is 3D-printed using fused deposition modeling (FDM) technology. The novel work can be extremely considerable in various medical and commercial applications.